Compact bent end electric lamp



I June 2, 1970 LA VERNE w sH ETAL 3,515,930

COMPACT BENT END ELECTRIC LAMP Filed July 31, 1968 Fig 1.

ITWVEfit'OTSI Laverne EWaLsh Gerahd W. Heimev United States Patent O U.S. Cl. 313220 7 Claims ABSTRACT OF THE DISCLOSURE In compact double-ended incandescent lamps, especially those of the halogen cycle type, having a pinch seal at each end of a quartz envelope and lead-in conductors extending through the pinch seals and including thin foil portions hermetically sealed in the pinch seals, especially wherein the pinch seals constitute a large proportion of the overall length of the envelope, the lamps are appreciably shortened by bending the pinch seals at the area of the foils so that the terminal end portions extend laterally of the envelope.

BACKGROUND OF THE INVENTION Field of the invention This invention relates generally to electric incandescent lamps and more particularly to compact incandescent lamps of the double-ended type having an envelope of essentially fused silica with a pinch seal at each end.

Description of the prior art There has been a need for lamps of the type described above and of shorter length. By concentrating the filament length in the form of a coiled coil, for example, it is possible to considerably reduce the envelope length. However, the pinch seal requires a foil of a minimum length to insure a hermetic seal, and the lead-in wires must be embedded for a minimum length to assure that they will be adequately anchored in the pinch seal. The pinch seals cannot therefore be reduced in length beyond a certain point, and the result is that in the case of short miniaturized lamps, the seals constitute a large proportion of the overall length of the lamp; in some cases the seals actually are of greater combined length than the envelope proper which contains the filament. Lamp length can of course, be decreased in some cases by using a single-ended construction which has a pinch seal at one end only of the envelope and through which both lead-in conductors extend. However, for certain applications it would be desirable to retain the double-ended construction if it could be shortened in overall length.

SUMMARY OF THE INVENTION It is accordingly an object of the invention to provide a double-ended lamp construction of shorter overall length, and more particularly to overcome the problem inherent in the long pinch seal at each end of the envelope.

In accordance with the invention, we have discovered that it is possible to bend the pinch seals at the area of the foils and still maintain a hermetic seal between the foil and the fused silica in which it is embedded. The bent terminal ends of the pinch seals may be made to extend laterally of the envelope axis in the same direction or in opposite directions, along with the ends of the lead-in conductors projecting exteriorly from the seals, thereby appreciably shortening the overall lamp length.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a top plan view, on an enlarged scale, of a lamp prior to the steps of bending the seals;

FIG. 2 is a side elevation of a lamp with bent ends in accordance with the invention;

FIG. 3 is a side elevation of the lamp of FIG. 2 mounted to extend horizontally in an outer reflector bulb;

FIG. 4 is a fragmentary side elevation of a lamp with its ends bent in opposite directions and mounted to ex tend vertically or axially in an outer reflector bulb; and

FIG. 5 is a side elevation of a lamp in accordance with the invention mounted in a conventional household type bulb.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The invention has particular application to lamps of the tungsten-halogen type, and the description will therefore be directed particularly to lamps of that type.

Referring to FIG. 1 of the drawing, the lamp illustrated therein comprises a tubular envelope 1 of essentially fused silica, including quartz glass and the product known as 96% silica glass and marketed under the name Vycor. The envelope 1 contains an axially extending coiled, preferably coiled-coil, filament 2 of tungsten which is connected at its ends to respective lead-in conductors each comprising an inner lead wire 3, preferably of tungsten, a seal portion 4 consisting of a thin foil of molybdenum, and an outer lead wire 5 which may be of molybdenum. The said lead-in conductors extend through respective flattened pinch seals 6 in which the foils 4 are hermetically sealed, and in which adjacent portions of the inner and outer leads 3 and 5 are embedded.

The envelope 1 contains a fill gas such as nitrogen, argon, krypton or xenon at a pressure, for example, of about 1 atmosphere, or preferably several atmospheres, and also a small quantity of a halogen such as iodine or bromine or compounds thereof. The lamp may be evacuated and filled by way of an exhaust tube, the residue of which is shown at 7.

Such a lamp is relatively quite compact since successful operation of the tungsten-halogen cycle requires it. For example, the envelope 1 for a 100 watt, volt lamp may have an outside diameter of about A inch and an internal length, between the pinch seals 6 of about /8 inch; and for a 250 watt, 120 volt lamp, the outside diameter of the envelope 1 may be about inch, and its internal length about "A; inch. However, in a conventional construction, the pinch seals 6 of the 100 watt lamp may each be about inch long, or a total length of pinch seals of about inch compared to about inch for the envelope proper. Similarly, in the 250 watt lamp, the pinch seals 6 may each be about /2 inch long, or a total of 1 inch compared to about Ms inch for the envelope proper.

However, for certain applications, it is desirable, or even necessary, that the lamp be shortened in length. In accordance with the invention, this is done by bending the pinch seals 6 to extend laterally of the longitudinal axis of the lamp as shown, for example, in the lamp designated L in FIG. 2 where the terminal ends of the pinch seals extend laterally in the same direction, as well as the outer lead wires 5. This may be done after the lamp has been otherwise completed, as shown in FIG. 1, by applying constricted but intense oxyhydrogen flames to opposite sides of a pinch 6 and across its width at substantially the midpoint of the length of a foil 4, and then bending the outer or terminal end of the pinch as seen in FIG. 2. The foil 4 extends around the curvature of the bend, and it bends with the softened quartz Without tearing the foil and without separation of the quartz from the foil, so that the hermetic seals are maintained.

The lamp construction of FIG. 2 is useful for mounting in a fixture by simply pushing the prong type rigid pins or leads 5 into the terminals of a receptacle or socket. It may be used, for example, in high intensity desk or table lamps in place of 12 volt automobile type lamps which are used at present and which require a transformer for operation from the ordinary household lines of 120* volts.

FIG. 3 illustrates another application of the lamp L of FIG. 2 where it is mounted within an outer bulb 8 which is in this case a well known projector lamp bulb designated PAR 38 and comprising pressed glass reflector and cover glass sections 9 and 10 respectively, which are fused together at their peripheries. The lamp L is mounted with its longitudinal axis extending transversely across the longitudinal axis of the bulb 8 and substantially in the focal plane or the modified paraboloidal inner refiecting surface 11.

The lamp L is supported by its outer leads 5 which may be provided with slip-over coils 12 and welded to the diverging ends of inner lead-in and support wires 13 which have their lower ends secured, for example by brazing, to the interior of metallic ferrules 14 which have their feather-edged rims sealed and embedded in the thickness of the base portion 15 of the bulb 8 around openings 16 through which extend the leads 13. Outer lead wires 17 and 1-8 are attached to respective ferrules and electrically connected to the screw-threaded shell 19 and to the end contact 20, respectively, of the base which includes a skirt portion 21 which fits snugly around the periphery of the base portion 15 of the bulb and is secured thereto, preferably by coacting dimples and depressions in said base portion 15 and skirt portion 21. A refractory insulating wafer or disc 22 is interposed between the lamp L and the bulb neck 15 to avoid overheating and damaging the seals of the ferrules 14 to the bulb neck. The bulb 8 is evacuated and filled with an inert gas such as nitrogen through an exhaust tube, the sealed otf residue of which is shown at 23.

It will be evident that a conventional lamp with straight pinch seals 6, as in FIG. 1, would not fit in the proper location in the conventional outer bulb 8. The position of the lamp L transversely of the longitudinal axis of the bulb 8 results in a spreading of the light beam projected thereby and is therefore useful for floodlighting applications.

The lamp L shown in FIG. 4 has respective pinch seals 6 bent to extend laterally in opposite directions. In this case the said lamp L is mounted with its longitudinal axis coincident with the longitudinal axis of the bulb '8 and its outer lead wires 5 secured to the ends of respective short and long lead-in conductors 13a and 13b. The filament 2 is thereby centered longitudinally about the focus of the reflecting surface 11 to produce a spotlight beam which is more concentrated than the beam produced by the FIG. 3 arrangement. It will be evident that the low placement of the lamp L in the bulb 8 would not be feasible if the lamp L had straight seal portions 6 as in 'FIG. 1.

In FIG. 5 there is shown a lamp L with seal portions 6 bent to extend in opposite directions, as in FIG. 4, and mounted vertically, or axially, in a conventional household type outer glass bulb 25. The said bulb 25 has a re-entrant stem 26 with a press seal portion 27 through which extend respective short and long lead wires 28 and 29 to which are secured the outer lead wires 5 of the lamp L The bulb 25 may be evacuated and filled with inert gas through the exhaust tube 30 which opens into the bulb interior by way of an aperture 31 in the press seal 27.

What we claim as new and desire to secure by Letters Patent of the United States is:

1. A compact high intensity electric lamp comprising a sealed envelope of essentially fused silica having a flattened pinch seal at each end thereof, a filament extending longitudinally of said envelope, a lead-in conductor connected to each end of said filament and extending through the proximate pinch seal to the exterior thereof, a portion of each said lead-in conductor being a metallic foil hermetically sealed in the associated pinch seal, each said pinch seal being bent at the area of the enclosed foil so that its terminal end portion extends laterally of the envelope.

2. A lamp as defined in claim 1 wherein the said terminal end portions extend laterally in the same direction.

3. A lamp as defined in claim 2 wherein the portions of the lead-in conductors which extend exteriorly of the pinch seals are sufiiciently rigidto support the lamp.

4. A compact lamp as defined in claim 3 and contained in an outer bulb having a longitudinal axis and rigid current supply conductors extending into said bulb at opposite sides of said axis, said compact lamp extending laterally across said axis of the outer 'bulb and supported from said current supply conductors by its exteriorly extending lead-in conductors.

5. A lamp as defined in claim 1 wherein the said terminal end portions extend laterally in opposite directions.

6. A lamp as defined in claim 5 wherein the portions of the leadin conductors which extend exteriorly of the pinch seals are sufiiciently rigid to support the lamp.

7. A compact lamp as defined in claim 6 and contained in an outer bulb having a longitudinal axis and rigid current supply conductors extending generally longitudinally into said bulb at opposite sides of said axis, said compact lamp extending axially of the outer bulb and supported from said current supply conductors by its exteriorly extending lead-in conductors.

References Cited UNITED STATES PATENTS 3,080,497 3/1963 Noel et al 313-220 X RAYMOND F. HOSSFELD, Primary Examiner U.S. Cl. XJR. 

